7 Risk Factors for Alzheimer’s Disease

What you should know

Despite tremendous advances in the understanding of Alzheimer’s disease, scientists have yet to pinpoint the causes of the disorder. Here’s what to know about each of the risk factors.

Older age

This is the strongest risk factor for Alzheimer’s disease. The likelihood of developing the disease doubles every five years beginning at age 65. After age 95, the risk reaches nearly 50 percent. Some evidence suggests that the number of new cases begins to drop off after age 90, though other research shows that it may increase.

Being a woman

Most researchers now agree that women are at higher risk for developing Alzheimer’s disease than men, even when women’s longer lifespans are taken into account. Researchers are studying whether decreased levels of estrogen after menopause are responsible or whether rising rates of vascular disease contribute.

Genetics

Having a family member who has Alzheimer’s increases the risk of developing the disease. However, only a handful of Alzheimer’s patients—fewer than 2 to 3 percent—have the disease as a result of a one of three identifiable defective genes (a gene mutation).

Down syndrome

The risk of Alzheimer’s disease is three to five times higher among people with Down syndrome than in the general population. The genetic abnormality responsible for Down syndrome is located on chromosome 21, the chromosome containing the amyloid precursor gene.

Head injury

There appears to be a strong link between serious head injury and risk of developing Alzheimer’s disease later in life. A moderate head injury (defined as a loss of consciousness for more than 30 minutes) is associated with a two times greater risk of developing the disease, and a severe head injury (defined as a loss of consciousness for more than 24 hours) is associated with a 4.5 times greater risk.

Depression

Several studies have suggested that experiencing depression may increase a person’s susceptibility to Alzheimer’s disease later in life. In one, researchers analyzed the results of several well-conducted studies and found that a history of depression doubled a person’s risk of developing Alzheimer’s disease.

Other possibilities

Other conditions that have been considered possible triggers of Alzheimer’s disease include immune system malfunctions, endocrine (hormonal) disorders, slow-acting viruses or bacteria, vitamin deficiencies, exposure to electromagnetic fields and accumulation of metals such as zinc, copper, iron and aluminum in the body. However, no solid evidence supports an association with any of these factors.

Health After 50, published by the University of California, Berkeley, School of Public Health, provides up-to-date, evidence-based research and expert advice on the prevention, diagnosis, and treatment of a wide range of health conditions affecting adults in middle age and beyond. It's part of Remedy Health Media's network of digital and print publications, which also include HealthCentral; HIV/AIDS resources The Body and The Body Pro; the UC Berkeley Wellness Letter; and the Berkeley Wellness website.